Thanks for the reply, Tim. Just curious - is that a hardware or a software limitation? One of the things I find really useful with the 6500 is being able to set it up as in the image below. To do that, I mix a 4m receive antenna with a broadband HF receiving loop on RX A, with the transmit antenna being a SG230 tuned doublet for the HF bands on ANT1 and the 70MHz amplifier path for 4m on the transverter port. I'm guessing I can achieve the same (and possibly better) on the 6400/6600 by dedicating one of the SCUs to a 4m transverter?